1. Field of the Invention
The present invention relates to a method of manufacturing a phase-change random access memory (PRAM) for storing data by changing a phase, and more particularly, a method of depositing chalcogenide which is a phase-change material.
2. Description of the Related Art
A PRAM uses a phase-change material of which the electrical resistance varies depending on an amorphous/crystalline state and the phase-change material may be chalcogenide (GST or Ge—Sb—Te; hereinafter, referred to as Ge—Sb—Te) including germanium (Ge), antimony (Sb) and tellurium (Te). Such a phase-change material is changed to the amorphous state or the crystalline state by heating or cooling. The resistance of the phase-change material is high in the amorphous state, but is low in the crystalline state. The values 0 and 1 of data can be identified by the change of the resistance. In order to grow a material Ge—Sb—Te which is the phase-change material, a sputtering method using the material Ge—Sb—Te as a target is generally used.
However, when a Ge—Sb—Te thin film is formed by the sputtering method, the composition of Ge, Sb and Te is very hard to be adjusted and a step-coverage is poor.